Cast-ibon ordnance



J.A.DAHLGREN. CAST IRON ORDNANGE.

Patented Aug. 6, 1861.

@@2172 ga/aga.- o A UNITED STATES OFFICE.

JOHN A. DAHLGREN, OI" PHILADELPHIA, PENNSYLVANIA.

CAST-IRON ORDNANCE.

Specification of Letters Patent No. 32,983, dated August 6, 1861.

T o all 'whom 'it Amay concern.:

Be it known that I, .loi-IN A. DAHLGREN, of the city and county ofPhiladelphia, in the State of Pennsylvania, have invented a new Fornifor Cast-Iron Ordnance, which consists in so shaping the gun as todispose all the metal available for the purpose about the part where thegreatest if not the whole force of explosion is exerted when the gun isdischarged, whereby I am enabled with a. given quantity and quality ofiron to make cannon which shall throw heavier' projectiles and a greateraggregate weight of them than cannon constructed by the rules hithertopracticed.

In the accompanying drawings, Figure 1 represents a side elevation of agun constructed in the improved form invented by me, and Fig. 2,represents a longitudinal section of the same.

For convenience of description I have divided the gun into four sectionsbounded as shown by the lines 1, 2 and 3 in Fig. 2. The part between theend of the breech and the line 1, I call the breech. The part betweenthe lines l and 2 I call the fort. The part between the lines 2 and 3, Icall the junction; and the part between the line 3 and the muzzle, Icall the chase. of measurement which I have employed for theconstruct-ion of the gun is the diameter of its bore,-or, as it isgenerally called, the caliber of the gun; and however large or small maybe the piece of ordnance which it is required to construct, thedimensions'of its several parts will be expressed in multiples orfractions of its own caliber corresponding to the proportions of the gunlaid down in F ig. 2, whose dimensions at important parts are denoted inunits of length equal to its own caliber.

Provided that, the quantity of powder with which the new gun is to betired bears the same relation to the weight of its projectile thatexists betwen the powder and projectile for which the gun shown in Fig.2, is designed; the proper weight of the projectile for which is a shellor hollow spher ical ball, about three quarters of the weight of a solidspherical ball of the same caliber to be tired with about one-seventhits weight The unit of powder. For example, it is required to make acannon having abore eight inches in diameter; the following dimensionsare ob- By the same rule also the weight of the projectile and of thepowder would be as follows, vizz Shell, empty 70 lbs. Powder A 10 lbs.

If however the weight of the charge of powder is to be materially lessthan one seventh to that of the shell or other projectile, then thediameters at 1 and 2 may be reduced to 2.909 calibei's, and the lengthof breech to 1.455 calibers, and the breech may have an ellipsoidalinstead of a spheroidal form. In like manner the dimensions in calibersof all the other parts may be obtained by measuring the drawing inFigj2.

In smooth-bored cannon the form of the breech may be hemi-spherical,hemispheroidal or ellipsoidal as greater or less strength is required.Strictly speaking, the surface of the fort should be curvilinearlongitudinally as well as transversely. But4 as artillerists insist onthe importance of having the means of taking a direct level aim forpoint blank tiring, in case of injury to the sights, the fort of thegun. represented in the drawings is made cylindrical the diameter beingfor that purpose slightly reduced between the points 1 and 2. Anotherdeviation from strict theoretic proportions is produced by a swell aboutthe muzzle, chiefly to protect it from liability to frac- CIL ture bybeing struck against, or by, hard bodies: this swell also answersanother purpose especially useful on board ships of giving a hold for alashing in case the gun is housed. v

The trunnions and other projections may be cast on, in the usual Way,but. the strength of the gun will be much increased if it is castWithout them; and they can be attached subsequently by a method., a moreparticular description of Which is given in another patent granted to meand bearing even date herewith.

That claim` as my invention and desire to secure by Letters Patent, ispA caste-iron gun constructed substantially according to the rule hereindescribed; whereby the quantities of metal disposed in the differentparts of the gun are proportionate, or nearly so, to the relativedegrees of strain exerted by the force of the eX- ploded charge at thoseparts respectively. JNO. A. DAHLGREN. lVitnesses JNO. D. BRANDT, A. B. NoR'roN.

